Abstract
For the first time, we investigated the effect of carbon nanotube (CNT) on surfactant/polymer flooding so as to improve oil recovery and explore its mechanisms. To this end, we performed wettability, surface tension (ST), and viscosity tests. Then, micromodel flooding was performed using design of experiments (DOE) method. The results demonstrated that the surfactant/polymer (SP) solution can reduce the contact angle from 143.6° to 24°; besides, the presence of nanopardcle in the solution approximates the contact angle to zero. Also, compared to the SP solution, the surfactant/nanoparticle/polymer (SNP) solution can lead to a more strongly water-wet surface wettability. In the case of SNP, increasing nanoparticle concentration slightly increases the fluid viscosity. Additionally, at fixed concentrations of surfactant and polymer, increasing nanoparticle concentration can raise ST values. Therefore, given the relationship between increasing ST and decreasing interfacial tension (IFT), it can be inferred that the presence of carbon nanotube in the SP solution can lead to a reduction in IFT. The emulsion tests illustrated that the presence of CNT in SP solution does not alter the emulsion type (water-in-oil). The results of micromodel flooding also showed that increasing the concentration of CNT in the SP solution improves oil recovery by 5-11%. Furthermore, an optimal concentration was defined for the surfactant in SNP flooding, up to which point increasing the surfactant concentration raises oil recovery but beyond which the oil recovery diminishes. The DOE method indicated that, in descending order, the polymer, CNT, and surfactant could have the greatest impact on boosting oil recovery. In other words, under SNP flooding, polymer concentration and surfactant concentration exert the most and the least impact on increasing oil recovery.
NSTL